boost/type_erasure/detail/normalize.hpp
// Boost.TypeErasure library
//
// Copyright 2011 Steven Watanabe
//
// Distributed under the Boost Software License Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// $Id$
#ifndef BOOST_TYPE_ERASURE_DETAIL_NORMALIZE_HPP_INCLUDED
#define BOOST_TYPE_ERASURE_DETAIL_NORMALIZE_HPP_INCLUDED
#include <boost/mpl/assert.hpp>
#include <boost/mpl/eval_if.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/mpl/is_sequence.hpp>
#include <boost/mpl/set.hpp>
#include <boost/mpl/map.hpp>
#include <boost/mpl/has_key.hpp>
#include <boost/mpl/insert.hpp>
#include <boost/mpl/vector.hpp>
#include <boost/mpl/back_inserter.hpp>
#include <boost/mpl/inserter.hpp>
#include <boost/mpl/fold.hpp>
#include <boost/mpl/transform.hpp>
#include <boost/mpl/copy.hpp>
#include <boost/mpl/at.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/type_erasure/detail/get_placeholders.hpp>
#include <boost/type_erasure/detail/rebind_placeholders.hpp>
#include <boost/type_erasure/detail/normalize_deduced.hpp>
#include <boost/type_erasure/relaxed.hpp>
#include <boost/type_erasure/builtin.hpp>
namespace boost {
namespace type_erasure {
template<class F>
struct deduced;
template<class T, class U>
struct same_type;
namespace detail {
struct substitution_map_tag {};
// a wrapper around an mpl::map that
// defaults to the identity map.
template<class M>
struct substitution_map
{
typedef substitution_map_tag tag;
typedef M map_type;
};
}
}
namespace mpl {
template<>
struct at_impl< ::boost::type_erasure::detail::substitution_map_tag>
{
template<class Seq, class Key>
struct apply
{
typedef typename ::boost::mpl::eval_if<
::boost::mpl::has_key<typename Seq::map_type, Key>,
::boost::mpl::at<typename Seq::map_type, Key>,
::boost::mpl::identity<Key>
>::type type;
};
};
template<>
struct has_key_impl< ::boost::type_erasure::detail::substitution_map_tag>
{
template<class Seq, class Key>
struct apply : boost::mpl::true_
{};
};
}
namespace type_erasure {
namespace detail {
// given a partial substitution map from same_type,
// resolves a placeholder as far as possible.
template<class M, class T>
struct resolve_same_type
{
typedef typename ::boost::mpl::eval_if< ::boost::mpl::has_key<M, T>,
::boost::type_erasure::detail::resolve_same_type<
M,
typename ::boost::mpl::at<M, T>::type
>,
::boost::mpl::identity<T>
>::type type;
};
// Given the arguments to same_type, determines
// which should be the key and which should be
// the value in the substitution map.
template<class T, class U>
struct select_pair
{
BOOST_MPL_ASSERT((::boost::is_same<T, U>));
typedef void type;
};
template<class T, class U>
struct select_pair<T, ::boost::type_erasure::deduced<U> >
{
typedef ::boost::mpl::pair< ::boost::type_erasure::deduced<U>, T> type;
};
template<class T, class U>
struct select_pair< ::boost::type_erasure::deduced<T>, U>
{
typedef ::boost::mpl::pair< ::boost::type_erasure::deduced<T>, U> type;
};
template<class T, class U>
struct select_pair<
::boost::type_erasure::deduced<T>,
::boost::type_erasure::deduced<U>
>
{
typedef ::boost::mpl::pair<
::boost::type_erasure::deduced<T>,
::boost::type_erasure::deduced<U>
> type;
};
// M is a map of placeholder substitutions
template<class M, class T>
struct normalize_placeholder
{
typedef typename ::boost::mpl::eval_if< ::boost::mpl::has_key<M, T>,
::boost::type_erasure::detail::normalize_placeholder<
M,
typename ::boost::mpl::at<M, T>::type
>,
::boost::mpl::identity<T>
>::type type;
};
template<class M, class T>
struct normalize_placeholder<M, ::boost::type_erasure::deduced<T> >
{
typedef typename ::boost::mpl::eval_if< ::boost::mpl::has_key<M, T>,
::boost::type_erasure::detail::normalize_placeholder<
M,
typename ::boost::mpl::at<M, T>::type
>,
::boost::type_erasure::detail::normalize_deduced<
M,
T
>
>::type type;
};
// Takes a mpl::map of placeholder substitutions and
// fully resolves it. i.e. a -> b, b -> c, becomes
// a -> c, b -> c. Also resolves deduced placeholders
// whose arguments are all resolved.
template<class M>
struct create_placeholder_map
{
typedef typename ::boost::mpl::fold<
M,
::boost::mpl::map0<>,
::boost::mpl::insert<
::boost::mpl::_1,
::boost::mpl::pair<
::boost::mpl::first< ::boost::mpl::_2>,
::boost::type_erasure::detail::normalize_placeholder<M, ::boost::mpl::second< ::boost::mpl::_2> >
>
>
>::type type;
};
template<class Bindings, class P, class Out, class Sub>
struct convert_deduced
{
typedef typename ::boost::type_erasure::detail::rebind_placeholders_in_argument<
typename P::first,
Bindings
>::type result1;
typedef typename ::boost::mpl::at<Sub, result1>::type result;
typedef typename ::boost::mpl::eval_if<
::boost::mpl::has_key<Out, typename P::second>,
::boost::mpl::identity<Out>,
::boost::mpl::insert<Out, ::boost::mpl::pair<typename P::second, result> >
>::type type;
BOOST_MPL_ASSERT((boost::is_same<typename ::boost::mpl::at<type, typename P::second>::type, result>));
};
template<class Bindings, class M, class Sub>
struct convert_deductions
{
typedef typename ::boost::mpl::fold<
M,
Bindings,
::boost::type_erasure::detail::convert_deduced<
Bindings, ::boost::mpl::_2, ::boost::mpl::_1, Sub
>
>::type type;
};
template<class Bindings, class P, class Out>
struct add_deduced
{
typedef typename ::boost::type_erasure::detail::rebind_placeholders_in_argument<
typename P::first,
Bindings
>::type result;
typedef typename ::boost::mpl::eval_if<
::boost::mpl::has_key<Out, typename P::second>,
::boost::mpl::identity<Out>,
::boost::mpl::insert<Out, ::boost::mpl::pair<typename P::second, result> >
>::type type;
BOOST_MPL_ASSERT((boost::is_same<typename ::boost::mpl::at<type, typename P::second>::type, result>));
};
template<class Bindings, class M>
struct add_deductions
{
typedef typename ::boost::mpl::fold<
M,
Bindings,
::boost::type_erasure::detail::add_deduced<
Bindings, ::boost::mpl::_2, ::boost::mpl::_1
>
>::type type;
};
// Fold Op for normalize_concept_impl
template<class Out, class T>
struct insert_concept
{
typedef ::boost::mpl::pair<
typename ::boost::mpl::insert<typename Out::first, T>::type,
typename Out::second
> type;
};
template<class Out, class T, class U>
struct insert_concept<Out, ::boost::type_erasure::same_type<T, U> >
{
typedef typename ::boost::type_erasure::detail::resolve_same_type<
typename Out::second,
T
>::type t1;
typedef typename ::boost::type_erasure::detail::resolve_same_type<
typename Out::second,
U
>::type t2;
typedef ::boost::mpl::pair<
typename Out::first,
typename ::boost::mpl::eval_if<
::boost::is_same<t1, t2>,
::boost::mpl::identity<typename Out::second>,
::boost::mpl::insert<
typename Out::second,
typename ::boost::type_erasure::detail::select_pair<
t1,
t2
>::type
>
>::type
> type;
};
// flattens a concept returning an mpl::pair
// - first is an MPL sequence containing the leaf concepts
// - second is an MPL map of the placeholder substitutions
// used to resolve same_type.
template<class Concept, class Out = ::boost::mpl::pair< ::boost::mpl::set0<>, ::boost::mpl::map0<> > >
struct normalize_concept_impl
{
typedef typename ::boost::mpl::eval_if< ::boost::mpl::is_sequence<Concept>,
::boost::mpl::fold<Concept, Out, normalize_concept_impl< ::boost::mpl::_2, ::boost::mpl::_1> >,
::boost::type_erasure::detail::insert_concept<Out, Concept>
>::type type;
};
struct append_typeinfo
{
template<class Set, class T>
struct apply
{
typedef typename ::boost::mpl::insert<
Set,
::boost::type_erasure::typeid_<T>
>::type type;
};
};
// Seq should be a flattened MPL sequence of leaf concepts.
// adds typeid_<P> for every placeholder used.
template<class Seq>
struct add_typeinfo
{
typedef typename ::boost::mpl::fold<
Seq,
::boost::mpl::set0<>,
::boost::type_erasure::detail::get_placeholders<
::boost::mpl::_2,
::boost::mpl::_1
>
>::type placeholders;
typedef typename ::boost::mpl::fold<
placeholders,
Seq,
::boost::type_erasure::detail::append_typeinfo
>::type type;
};
template<class Concept>
struct get_placeholder_normalization_map
{
typedef typename ::boost::type_erasure::detail::create_placeholder_map<
typename normalize_concept_impl<Concept>::type::second
>::type type;
};
// Flattens a Concept to an mpl::vector of primitive
// concepts. Resolves same_type and deduced placeholders.
template<class Concept>
struct normalize_concept
{
typedef typename normalize_concept_impl<Concept>::type impl;
typedef typename ::boost::type_erasure::detail::create_placeholder_map<
typename impl::second
>::type substitutions;
typedef typename ::boost::mpl::fold<
typename impl::first,
::boost::mpl::set0<>,
::boost::mpl::insert<
::boost::mpl::_1,
::boost::type_erasure::detail::rebind_placeholders<
::boost::mpl::_2,
::boost::type_erasure::detail::substitution_map<substitutions>
>
>
>::type basic;
typedef typename ::boost::mpl::eval_if<
::boost::type_erasure::is_relaxed<Concept>,
::boost::type_erasure::detail::add_typeinfo<basic>,
::boost::mpl::identity<basic>
>::type concept_set;
typedef typename ::boost::mpl::copy<
concept_set,
::boost::mpl::back_inserter< ::boost::mpl::vector0<> >
>::type type;
};
// Returns an MPL sequence containing all the concepts
// in Concept. If Concept is considered as a DAG,
// the result will be sorted topologically.
template<
class Concept,
class Map = typename ::boost::type_erasure::detail::create_placeholder_map<
typename ::boost::type_erasure::detail::normalize_concept_impl<
Concept
>::type::second
>::type,
class Out = ::boost::mpl::set0<>
>
struct collect_concepts
{
typedef typename ::boost::type_erasure::detail::rebind_placeholders<
Concept,
::boost::type_erasure::detail::substitution_map<Map>
>::type transformed;
typedef typename ::boost::mpl::eval_if<
::boost::is_same<transformed, void>,
::boost::mpl::identity<Out>,
::boost::mpl::insert<
Out,
transformed
>
>::type type1;
typedef typename ::boost::mpl::eval_if< ::boost::mpl::is_sequence<Concept>,
::boost::mpl::fold<Concept, type1, collect_concepts< ::boost::mpl::_2, Map, ::boost::mpl::_1> >,
::boost::mpl::identity<type1>
>::type type;
};
}
}
}
#endif